cam is exactly right. I had to upgrade the WLC to 7.0.xx to gain functionality that allows clients to fall back to Web Authentication after MAC authentication fails.
The only caveat that I would add is this. The WLC will ONLY pass the MAC with all letters being lowercase. By default the Aruba wants to send the MAC with uppercase letters. And Amigopod only accepts MACs with capital letters...
So, I had to change the Aruba controller to send in lowercase, then I modified the guest account creation form in Amigopod to accept lowercase letters in the MAC. To change that form in the Amigopod i basically had to turn off the "NwaNormalizeMacAddress" code that it ran the MAC through...
It was a messy config full of trial and error, but now that its done it works very well. Maybe a step by step guide is in order? ;)